1. Field of the Invention
The present invention relates to a nut, a nut and panel assembly, the method of assemblying the nut and panel, and the piercing tool for assembling same. More particularly, the invention relates to a nut having a counterbore indent terminating in a crown-shaped configuration for receiving panel material to stabilize the nut against the panel when a bolt is threaded into the nut and panel.
2. The Prior Art
The prior art includes the disclosure of a nut and panel assembly, wherein the nut includes a first circular bore for threadedly receiving a bolt and a counterbore tapering toward the nut face abutting the panel, as disclosed in U.S. Pat. No. 3,282,317 to Zahodiakin. The primary purpose for the tapering counterbore is to stabilize the nut on the metal panel assembly against axial displacement due to the push-off forces encountered when a self-tapping bolt, or the like, is threaded into the nut bore. Such an arrangement, however, does not preclude rotational displacement of the nut during the threading operation, which can cause cross-threading. Further, because the self-tapping bolt threads directly into the nut bore, the nut can be axially displaced from the panel even in view of the tapering counterbore locking arrangement.
Other prior art patents, for example as illustrated by U.S. Pat. No. 3,234,987 to Hentzi, disclose a nut configuration including a plurality of radial serrations for stabilizing the nut on the panel against rotational displacement during the threading operation. The Hentzi patent further includes the provision of a deformed nut edge for stabilizing the nut on the panel against axial displacement. However, the Hentzi patent discloses a nut having a threaded bore for receiving a male bolt member, rather than a circular bore for receiving a selt-tapping bolt member, as contemplated in one of the preferred embodiments of the present invention. Should the Hentzi nut be employed in combination with a self-tapping bolt, it is quite probable that the nut would become displaced either axially or rotationally since the axial threading forces would be applied directly to the nut.
The present invention overcomes the prior art problems of nut rotational and axial displacement by the provision of a counterbore terminating in an annular face having a hill-and-valley configuration. Panel material circumscribed by the nut counterbore is pierced and deflected into the shape of an annular projection terminating in an end portion conjugate with and adjacent to the counterbore annular surface. The interlocking crown relationship between the nut counterbore and the deflected panel material stabilizes the nut against rotational and axial displacement during a bolt threading operation.
Other prior art patents, for example U.S. Pat. No. 2,004,182 to Arey, disclose piercing a panel and deflecting the panel material to assume a jagged end configuration. However, the Arey patent does not control the breakout of the pierced panel material, in contrast to the present invention which deflects the panel material into a counterbore terminating in an annular surface conjugate the terminal end of the panel breakout to stabilize the nut against rotational displacement during a self-tapping operation.